This invention relates generally to injection molding and more particularly to a heated nozzle with an electrical terminal having an electrically insulative connector.
Injection molding nozzles having an integral electrical heating element extending to a terminal are well known in the art. The diameter of the conductive wire in the heating element must be larger adjacent the terminal to avoid excessive heat at the terminal. The conductive wire must be electrically connected at the terminal to an external lead or leads and be electrically insulated from the nozzle body which is made of steel.
In the past, this has been provided for low voltage nozzles with only a single external lead by having a layer of insulation between an inner portion of the terminal and an outer portion to which the conductive wire and external lead are both connected. This is shown in U.S. Pat. No. 4,837,925 to Gellert which issued Jun. 13, 1989. Nozzles having terminals to connect both ends of the electrical heating element to separate external leads are more difficult. In addition to overcoming the above problems, electrical separation must be maintained between the two leads and between the two outer end portions of the conductive wire. Also connecting and disconnecting of the external leads must be facilitated, and the terminal must have sufficient structural strength to avoid bending or breaking when this is done. Gellert Canadian patent application serial number 2,057,594-8 filed Dec. 13, 1991 entitled "Method of Making an Injection Molding Nozzle with a Single Heating Element in a Double Channel" shows a nozzle with a terminal for connecting a pair of external leads. Each lead extends into a longitudinal bore in a connector where its bared inner end portion overlaps a respective outer end portion of the conductive wire and they are secured together by a set screw which is screwed into the connector. However, the connector is made of metal and therefore must be surrounded by a separate insulator made of a ceramic material. In addition to requiring the manufacture of both connectors and insulators, this has the disadvantage that installation is relatively difficult because the transverse openings in the insulator must be aligned with the transverse openings in the connector. Also, the terminal must be long enough to allow the insulator to extend out past the metal connector at both ends, and it is difficult to seal the outer end of the terminal against moisture.